The internal combustion engine of a vehicle transmits power to the vehicle via a transmission train comprising a gearbox and a clutch, which are normally operated by the driver of the vehicle. Power-assisted manual shifts, however, are becoming increasingly popular, and which are structurally similar to a conventional manual shift, except that the driver-operated control pedals and levers are replaced by corresponding electric or hydraulic servocontrols. Using a power-assisted manual shift, the driver simply sends an up- or downshift command to a central control unit, which automatically shifts gears by acting on the various servocontrols.
When a gear shift is commanded by the driver, a clutch servocontrol releases the clutch, a shift servocontrol makes the desired gear shift, and the clutch servocontrol re-engages the clutch. The servocontrols are obviously controlled and operated using sensors for real-time determining the values of various reference quantities of the gearbox-clutch system.
A power-assisted manual gearshift is typically expected to provide for both dynamic performance and passenger comfort, which call for fast gear shifting with no passenger-perceptible oscillations. To achieve this, correct clutch position control is essential, in that both shift time and any oscillations produced are determined by operation of the clutch. Currently marketed hydraulic-actuator-powered clutches, however, fail to provide for correct clutch position control in all operating conditions.